The present invention relates to pneumatic tires used on passenger vehicles, and particularly to geodesic tires having carcass plies following geodesic paths.
In conventional pneumatic tires for passenger vehicles, the main internal structure or carcass of the tires includes a pair of beads and a plurality of plies wrapped from the first bead to the second bead to define a generally U-shaped cross-section. The plies are rubber-coated fabric cords composed of materials such as polyester. The plies are typically wrapped to extend either generally perpendicular to the pair of beads or angled to the pair of beads (referred to as a “bias” construction). The plies define the primary structural component of a pneumatic tire and transfer forces from a tread of the tire to the beads and therefore the rims of the tire. Ply construction is well known in the art and is generally successful for its intended purpose, which is to maintain the size and shape of the tire and transfer loads applied to the tire.
Geodesic Tires are those tires whose ply cord paths are geodesic lines on the tire surface. More specifically, a geodesic tire includes angled ply cords that have a small angle of inclination from a tangential direction near the beads and a larger angle of inclination at the crown portion of the tire. This ply cord path leads to improved durability and an improved or soft ride. The field of ply winding machines has advanced to a point that pneumatic tires having substantially geodesic plies can be generated using sophisticated computerized controls of the ply winding machine. However, the operation of these machines is highly complex and time consuming, which significantly increases the expense of manufacturing truly geodesic tires. There is a need, therefore, for an improved pneumatic tire that addresses these and other issues associated with conventional tires.